1. Technical Field
The invention relates to radio frequency (RF), microwave and millimeter wave circuits and systems. In particular, the invention relates to detectors used with RF, microwave and millimeter wave signals.
2. Description of Related Art
Radio frequency (RF) detectors, microwave detectors and millimeter wave detectors are circuits used to rectify and detect RF, microwave and millimeter wave signals, respectively. In some examples, RF/microwave/millimeter wave signal detection may be used to determine a power level of an RF/microwave/millimeter wave signal. In these examples, the RF/microwave/millimeter wave detector acts as a power detector. In other examples, the RF/microwave/millimeter wave detector may be employed to detect an amplitude modulation of the RF/microwave/millimeter wave signal. In particular, the RF/microwave/millimeter wave detector may be used to demodulate the amplitude modulation and produce a baseband or video signal representing an envelop of the amplitude modulation, for example. As such, RF/microwave/millimeter wave detectors are also sometimes characterized as ‘envelop’ detectors.
A variety of RF/microwave/millimeter wave detectors has been developed including various detectors based on or using detector diodes. Detector diodes used in RF/microwave/millimeter wave detectors are typically semiconductor diodes having a relatively low junction capacitance and a high sensitivity in frequency ranges (e.g., RF, microwave and/or millimeter wave) of interest. Examples of semiconductor diodes that are often used as detector diodes include, but are not limited to, Schottky diodes (both zero-bias and biased), planar doped barrier diodes, and backward tunneling or Esaki diodes. Unfortunately, many RF/microwave/millimeter wave detectors have a relatively limited operational bandwidth. In particular, it may often be difficult to achieve wideband impedance matching in conventional diode-based detector circuits leading to the limited operational bandwidth. The wideband impedance matching may be limited due to an inherent reactance (e.g., junction capacitance) of the diodes employed in the RF/microwave/millimeter wave detector, for example.